微波法制备人造金红石新工艺及设备研制

【作者】 陈菓；

【导师】 彭金辉；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2012， 博士

【摘要】 天然金红石和人造金红石是盐酸法和硫酸法生产二氧化钛(TiO2)颜料的重要原料之一。目前,可利用的高品位天然金红石的供应量急剧减少,探索一种在较低的能源消耗和较小的环境污染下生产人造金红石的方法已经日趋迫切。因此,从可以大量利用的钛渣资源中制备人造金红石成为一种发展趋势。微波加热技术广泛地应用到实验研究和工业生产过程中,与传统加热技术相比,微波加热的主要优势是内部加热和整体加热,因此加热过程非常迅速,从而节约能源和缩短处理时间。微波加热具有较高的电磁转换效率,加热效率高。此外,微波加热设备的尺寸较小,被加热材料和微波源之间不直接接触,是一种清洁、绿色的生产模式。本论文根据云南省生产的高钛渣的结构与特征,提出一种微波加热—选矿联合工艺制备高品质的人造金红石产品的新工艺,并与常规加热方式进行了对比。高钛渣在微波加热和传统加热前后的化学成份,晶体结构,显微结构和表面官能团通过X射线衍射,扫描电子显微镜,能谱分析,拉曼光谱,傅立叶变换红外光谱等方法进行分析。高钛渣的主要成分为钛的氧化物、FeO、A1203、SiO2、MgO和MnO，以及硫、磷、碳等少量元素。XRD分析结果表明,高钛渣的主要物相是锐钛型TiO2和Fe3Ti3O10(M3O5型黑钛石固溶体),以及少量的金红石型TiO2SEM-EDAX分析结果表明,高钛渣表面比较光滑,样品表面出现明显的凹陷和条状裂痕。FT-IR光谱分析结果表明,493.3cm-1处的特征峰是因为高钛渣Ti O2的Ti-O和Ti-O-Ti伸缩振动形成的。Raman光谱分析结果表明,在155.2,195.8,393.7,515.5and637.3cm-1处出现锐钛型TiO2,Ti3O5,Ti2O3的拉曼振动模式特征峰。热分析结果表明,高钛渣在850℃左右出现了放热峰,说明在此温度范围,锐钛型TiO2开始不可逆地转变为金红石型TiO2。影响锐钛矿TiO2向金红石TiO2变的实验条件主要包括：温度,颗粒大小,氧化物的合成方法等。采用微波谐振腔扰动技术测试了高钛渣的微波吸波特性。通过分析和计算微波波谱图中波谱的相对频率移动和电压振幅,得到测试样品的微波吸收性能。并测试了高钛渣在微波场中的升温曲线。系统研究了不同粒度的高钛渣、混合不同含量V2O5、微波焙烧前后对样品的微波吸波特性的影响。测试结果表明,高钛渣具有较强的微波吸收能力,能够在微波场中迅速地被加热。当高钛渣粒度为180μm,混合V205的含量为10%时,在各自的微波波谱图中,具有较大的相对频率移动和较低的电压振幅,此时为不同条件下样品吸波特性测试的最佳条件在微波加热过程中,系统研究了微波焙烧温度和保温时间对二氧化钛品位,硫、碳含量和Ti02晶型转变的影响。随着微波加热温度和保温时间的增加,二氧化钛品位和硫、碳含量都呈减少的趋势,与常规加热相比,时间缩短。从XRD中可以看出,金红石Ti02的(101),(111)和(211)晶面的衍射峰强度逐渐增加,锐钛型Ti02和Fe3Ti3O10的各个晶面的衍射峰强度逐渐降低。Raman结果表明,位于396.8,515.2,637.0cm-1为锐钛型Ti02的拉曼振动模式特征峰强度逐渐减少,位于153.2cm-1为Ti305的拉曼振动模式特征峰消失,位于197.2cm-1为Ti2O3的拉曼振动模式特征峰消失。位于244.6,445.6,615.0cm-1为金红石型TiO2的拉曼振动模式特征峰的强度逐渐增加,并移至低波数,产生红移。FT-IR结果表明,在1697.Ocm-1处的吸收峰为样品中所含水分的H-O-H的弯曲振动吸收峰消失,在1089.6cm-1处为O-H键的弯曲振动吸收峰减弱,在529.3cm-1处为TiO2八面配位体的振动引起的特征峰移至高波数,产生蓝移。SEM结果表明,经过微波处理后的样品呈现出不规则的针状结构,在样品的表面上很多的孔被打开,导致了样品的表面积增大。样品中的其他杂质如锰、镁、硅等富集在灰白色的小颗粒中,有利于下一步的选矿分离过程。选择微波加热温度,微波功率和保温时间作为自变量,人造金红石含量作为因变量,采用响应曲面法(RSM)和中心组合设计(CCD)对微波加热焙烧高钛渣制备人造金红石工艺进行参数优化设计。采用最小二乘法和非线性回归分析实验结果,得到因变量与自变量的二阶多项式,该模型的相关系数值R2为0.9691,校正决定系数值adj.R2为0.9382,说明各个自变量独立作用于因变量。失拟项F-value为3.47,说明失拟项相对于纯误差不具有显著性。变异系数CV为0.45%,说明了设计的条件实验具有较高的精度和较好的可靠性。通过对非线性回归方程的求解和对响应曲面和等高线的分析,得到微波焙烧高钛渣的最佳工艺参数为：焙烧温度936℃,微波功率2.5kW,保温时间48min。在此工艺条件下的试验值与预测值比较接近,误差较小为了提高微波焙烧产物中Ti02的含量,采用选矿工艺除去其中的杂质。探索球磨时间,磁场强度,浮选药剂等因素对微波焙烧产物中二氧化钛含量的影响。当磨矿时间为60min,磁选电流为5A,抑制剂CMC的用量选用为250g/t,捕收剂羟肟酸的用量选用为300g/t,产品的二氧化钛品位达到91.25%,满足国家人造金红石行业标准中优级品标准。本课题从微波焙烧高钛渣的反应过程对微波高温管式反应器的性能的需求,根据电磁场理论,设计得到微波谐振腔的尺寸。通过分析计算结果,设计出矩形波导的内截面尺寸,以确保微波能以最佳的传输效率进入微波谐振腔。合理选择功率馈口,使得微波能够在微波谐振腔内形成多种模式分布,从而获得微波场强均匀、功率密度大的微波场。通过非相干功率合成技术,微波功率源由2只频率为2450MHz,功率为1.5kW的磁控管组成,并采用水循环冷却的方式。此外,该微波高温管式反应器还包含了阳极电源、灯丝电源、电气系统以及磁控管和电器元件的冷却系统。因此,微波高温管式反应器能够在高温条件和高功率密度下进行连续工作。选用低介电常数、低功率损耗、低热膨胀系数的微波专用陶瓷管,并采取多种保温材料保温。采用K型热电偶测量温度,并置于接近样品的位置。热电偶提供的反馈信号用于控制磁控管的功率,调节微波加热过程中的温度,防止过热现象。采用Solid edge三维设计软件对微波高温管式反应器的微波谐振腔、矩形波导、功率馈口及其附属零部件进行建模、优化设计、模拟装配。采用层次分析法和模糊综合评价法对微波高温管式反应器的生命周期进行了分析和评价。选择环境属性,资源属性,经济属性,性能属性和功能属性作为评价指标,系统地研究了评价指标对评价模型的影响。评价过程涉及到层次结构的建立,评价标准的建立,选择权重矩阵,两两对比矩阵的建立和模糊评价矩阵的建立,采用模糊数学方法和统计方法计算微波高温管式反应器的绿色度结果。结果表明研制的微波高温管式反应器具有很好的绿色度,满足绿色制造的目标,特别在能源消耗,处理时间和环境污染方面具有较好的效果。通过采用层次分析法和模糊分析法对微波高温管式反应器进行生命周期评价,能够提供了一种在较低的资源消耗和较少的环境污染下研制微波高温管式反应器的方法。更多还原

【Abstract】 Titanium dioxide pigments are manufactured by the chloride or sulfate processes, in which natural rutile or synthetic rutile is used as raw materials. Since available resources of high grade natural rutile tend to diminish, to explore new method to produce synthetic rutile with low energy consumption and less environment pollution is necessary. Thus, producing synthetic rutile from abundantly available high titanium slag becomes a major alternative.Microwave heating has been widely used in research and industrial processes. Compared with conventional heating techniques, the advantage of using microwave heating is that microwave heating is both internal and volumetric heating. Therefore, microwave heating is very rapid, resulting in energy savings and shortening the processing time. Since microwave heating has a high efficiency to convert electricity energy to electromagnetic energy. Additional advantages include greater control of the microwave heating process, no direct contact between the heating source and heated materials and reduced equipment size, which can fulfil the mode of green and clean manufacturing.The work addresses preparation of a new method for high grade synthetic rutile using combined microwave heating and mineral processing technology. The new processing was basically in accordance with the structure and characteristic of high titanium slag from Yunnan Province. The thermal stability, crystal structures, microstructure, surface chemical functional groups and molecular structures of samples were characterized by thermogravimetry and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR) and Raman spectroscopy techniques, respectively. High titanium slag mainly contains iron titanium oxide, FeO, Al2O3, SiO2, MgO, MnO, and minor elements, such as S, P and C. It can be seen from XRD results that anatase TiO2and Fe3Ti2O10(anosovite-type of M3O5) were mainly crystalline compounds in high titanium slag. In addition, a minor amount of rutile TiO2was present. From the SEM-EDAX, the results indicated that the surface structure of primary particles with tighter and smoother surface morphology could be observed in the samples. And more fine cracks could be found on the surface from the SEM image. It has confirmed from FT-IR that the IR bands at493.3cm-1could be ascribed to the bending vibrations of Ti-O and Ti-O-Ti of the TiO2units. The Raman spectrum of the samples showed peaks at155.2,195.8,393.7,515.5and637.3cm-1which were directly attributable to anatase, Ti2O5, and Ti2O3. DTA curve analyses show the exothermic peaks at850.0℃, the thermal analysis results indicate that the anatase TiO2was irreversible conversion to the rutile TiO2in this temperature range. The transformation of anatase TiO2to rutile TiO2was influenced by several experimental conditions, such as temperature, particle size and synthetic method of dioxide.Microwave absorbing properties of high titanium slag were investigated using microwave cavity perturbation technique. By analyzing of the changing behavior and calculating the amplitude of voltage and the shift of frequency of the microwave spectrums, the microwave absorbing properties of samples were obtained. The temperature rise curve of high titanium slag in microwave heating process was acquired. Effects of particle size of high titanium slag and mixtures of high titanium slag with different mass fractions of V2O5on microwave absorbing properties were investigated systematically. The results show that high titanium slag has good microwave absorption property, and it can be heated effectively and efficiently in the microwave field. High frequency shift and low amplitude of voltage make high titanium slag an ideal microwave absorbent.180μm of particle size and10%mass fraction of V2O5were found to be the optimum conditions for microwave absorption, respectively.The effects of microwave heating temperature and holding time on the crystal phase transformation of TiO2, content of TiO2, sulfur content and carbon content were systematically investigated under microwave heating processing. With increasing microwave heating temperature and holding time, the content of TiO2, sulfur content and carbon content decreases, shorten processing time remarkably compared to conventional heating. It can be observed from XRD that the intensity of diffraction peak of the lattice planes (101),(111) and (211) of rutile TiO2were increased and the intensity of diffraction peak of anatase TiO2and Fe2Ti2O1o were decreased. With increasing microwave heating temperature and holding time, the content of TiO2, sulfur content and carbon content decreases, shorten processing time remarkably compared to conventional heating. The intensity of Raman vibrations bands of anatase TiO2at396.8,515.2and637.0cm-1decrease, the intensity of Raman vibrations bands of Ti3O5and the intensity of Raman vibrations bands of Ti2O3at153.2cm-1and197.2cm-1disappears, respectively. And the intensity of Raman vibrations bands of rutile TiO2at244.6,445.6and615.0cm-1increase, and the peaks individually redshifts to low-wave number after microwave irradiation. It can be observed from FT-IR that the most obvious change in the spectrum is that the absorption band the bending vibrations of H-O-H at1697.0cm-1disappears, and the bands of the bending vibrations of O-H at1089.6cm-1become barely visible, and the stretching vibrations of octahedral metal ion in the TiO2units at529.3cm-1individually blueshift to high-wave number. From the SEM image, the results indicated that microwave treated samples appears irregular with a complex acicular structure. The pores of samples surface can be opened through microwave irradiation, which lead to increased surface area. The impurity minerals such as Si, Al, Mg and Mn in the samples have been enriched into the gray granule. They were propitious to the minerals separation processing.Microwave heating temperature, microwave power, and time were the main three dominant factors selected as independent variables. Synthetic rutile content was selected as a dependent variable affected by these factors. Response surface methodology and central composite design were implemented to optimize the experimental conditions for preparing synthetic rutile from high titanium slag by microwave irradiation. By applying least squares method and multiple regression analysis on the experimental results, the second order polynomial equation was found to explain the dependent variable by considering the independent variable. The coefficient of determination (R2) of the model was obtained0.9691, and the value of the adjusted determination coefficient (adj.R2) was0.9382, which suggested that there were excellent correlations between the independent variables. The F-value of the lack-of-fit of3.47implies the lack-of-fit is significant relative to the pure error. In the present case, a very lower value of CV (0.45%) clearly showed a high degree of precision and a good deal of reliability of the experimental values. The optimum experimental conditions of microwave roasting high titanium slag obtained from solving nonlinear regression equation and analyzing response surface and contour. These optimal conditions were microwave temperature of936℃, microwave power of2.5kW, and holding time of48min. Only small deviations were found between the experimental values and the predicted values.In order to improve the quality of TiO2, the minerals separation processing has been proposed for removing the impurity minerals from the microwave roasted production. The effects of milling time, magnetic field strength and flotation reagent on titanium dioxide of microwave roasted samples. Milling time of60min, magnetic field electric current of5A, CMC inhibitor used in flotation separation of250g/t. hydroximic a cid catching agent used in flotation separation of300g/t, the titanium dioxide content of91.25%was obtained, while the synthetic rutile reaches the National Class I Standard.The requirements of the reaction behaviour of microwave high temperature tube reactor during the actual reaction of microwave roasting high titanium slag were studied in this article. According to the classical electromagnetic theory, the sizes of the microwave resonant cavity were designed. In order to make sure that microwave will efficiently transfer into the microwave resonant cavity, the cross-section size of the rectangular waveguide were obtained on the basis of an analysis of calculation results. We can adopt a reasonable choice for the power transmission, it would ensure that microwave were distributed in various patterns in the microwave resonant cavity and obtained a uniform and power microwave field. The microwave power supply for the microwave high temperature tube reactor was made of2magnetrons using the non-coherent power synthesis of power technology, which was cooled by water circulation, at2.45GHz frequency and1.5kW power. The microwave high temperature tube reactor consists of an anode power, a filament power, an electrical systems and a cooling system of the magnetron and the electrical components. Therefore, the microwave high temperature tube reactor can work continuously at high temperature conditions and high power density. Considering the integrated requirements of low dielectric constant, low power consumption and low heat expansion coefficient, the special microwave ceramic tube was selected with different thermal insulation material. The temperature was measured using a Type K thermocouple, placed at the closest proximity to the sample. The thermocouple provides feedback information to the control panel that controls the power to the magnetron, controlling the temperature of the sample during the microwave treatment process in order to prevent the sample from overheating. Modelling, optimization design and simulating assembly of microwave resonant cavity, rectangular waveguide, power transmission and it spare and accessory parts of the microwave high temperature tube reactor using Solid Edge3D design software.In this study, analytic hierarchy process and fuzzy comprehensive evaluation were implemented to the analyzed and assessed for the life cycle assessment of microwave high temperature tube furnace. The effects of the evaluation aspect, such as environmental impact, resource consumption, economy, capability and function, on the mathematical model were systematically investigated. The process involves constructing hierarchical structure, comparing pairwise comparison matrices, establishing assessment criteria, setting weight matrix and fuzzy assessment matrix, and then calculating green degree of microwave high temperature tube furnace by fuzzy mathematical method and statistical technique. The results show that microwave high temperature tube furnace has a good green degree, which can be fulfill with the aim of green manufacture, especially in energy consumption, processing time and environmental protection. Life cycle assessment of microwave high temperature tube furnace using analytic hierarchy process and fuzzy comprehensive evaluation was an easy and practical way to provide a mechanism for improving microwave high temperature tube furnace quality with low resource consumption and less environment pollution.更多还原